A known door hinge for recessed installation between an edge of a door panel and a door jamb has first and second leaf assemblies that each form a cavity and are recessed in the door-panel edge and in the door jamb. A pair of U-section links pivoted centrally together about a center axis each have a first end and a second end engaged in the cavities of the respective first and second leaf assemblies. The first end of one of the links and the second end of the other link are pivoted about respective vertical axes fixed in the respective leaf assemblies and the second end of the one link and the first end of the other link are pivotal about another respective vertical axis and horizontally shiftable in a respective guide of the respective leaf assemblies. Thus when the assemblies are fitted to respective mortises in the jamb and door edge, when the door is closed the hinge is not visible.
As described in U.S. Pat. No. 6,829,808, one of the links is forked and partly U-shaped and the other of the links projects between the legs of the U. Thus the first end of the other link is substantially vertically shorter than the first end of the one link. The problem with this construction is that when used with a very heavy door, the links can deform, as they are not highly rigid and are not supported except at the pivot in the respective leaf assembly,
Another door hinge with the above-described features is known from U.S. Pat. No. 7,861,378 where the hinge links are designed as constructionally identical U-shaped mounting elements with a connecting bight and vertically aligned legs. In order to be able to connect the physically identical hinge links to each other, one of the hinge links is rotated by 180° so that starting from the connecting bight, the vertically aligned legs of the rotated hinge link do not extend upward but downward. The two hinge links can then be joined together in the manner like a plug connector. The seat cavities of the leaf assemblies are completely bridged by the legs extending in the vertical direction. However, due to the U-shape, a certain elasticity remains between the vertically aligned legs and the connecting bight arranged therebetween, even in the case of a very heavy weight load.
A further door hinge of this type is known from U.S. Pat. No. 6,487,755. Here one half of each hinge link extends vertically along the door hinge, and to adjust the height of the door panel, the spacing between the hinge links can be changed. For this purpose, the pivot pin between the hinge links is formed as an adjusting spindle. The dimensional stability of the known arrangement needs improvement. This door hinge is suitable for installation in light door panels, for example in the furniture sector.